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PURPOSE:

The aim of the present study was to evaluate the effect of heavy resistance training on maximal and ‘explosive' muscle strength, soccer performance and muscle morphology of female elite soccer players.

METHODS:

16 players were tested at end of autumn season (P1), after 12 weeks of either isolated heavy resistance training (1.7 sessions/wk) (HRT) or detraining (CO) (P2), and at end of the following spring season (P3). Isokinetic eccentric and concentric strength was measured in a Kincom. Explosive strength was determined as the contractile Rate of Force Development (RFD) in maximal isometric contraction. Sprint, countermovement jump, and kicking performance were measured. Histochemical analyses were performed to identify fibre type composition and fibre area (type I, IIA and IIX). Non-parametric tests were used for statistical analyses.

RESULTS:

At P2, the HRT group increased maximal eccentric quadriceps muscle strength and RFD (p < 0.05). A significant decrease in RFD of the hamstrings was observed in the CO group (p < 0.05). At P2, an increase in percentage of type IIA fibres with a corresponding decrease in type IIX fibres were observed for the HRT group (p < 0.05). Fibre area of type IIA and IIX increased in the HRT group, and the fibre area of type IIX decreased in the CO group (p < 0.05). The HRT group improved jump, sprint and kicking performance significantly at P3.

CONCLUSIONS:

Heavy resistance strength training induced significant increases in maximal eccentric and explosive quadriceps strength. Soccer performance improved only when resistance training was followed by a period of soccer training. Strength increases were accompanied by fibre type transformation from IIX towards IIA and hypertrophy of type IIA and IIX muscle fibres. 12 weeks of detraining induced a significant decrease in RFD of the hamstrings in the CO group. A decrease in RFD of the hamstrings could be a potential risk factor for knee injury in fast and explosive movements.